Bicycle crank assembly

ABSTRACT

An improved bicycle crankshaft assembly, including a crank axle with an axial axle axis, a first axle end, and a second axle end axially opposed to the first axle end; a first crank arm connected to the crank axle at a first crank arm interface adjacent the first axle end; a second crank arm connected to the crank axle at a second crank arm interface axially spaced from the first crank arm interface; a first bearing surrounding said crank axle adjacent said first axle end for rotation of said crank axle about said axial axis; a second bearing surrounding the crank axle and axially spaced from the first bearing. The crank axle includes reinforcement fibers for structural reinforcement of the crank axle and the crank axle is an integral crank axle that simultaneously contacts both the first bearing and the second bearing.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of U.S. provisional patent application60/628,773, filed Nov. 17, 2004, and entitled “Crank Axle Assembly”.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention is related to the crank axle of a bicycle crank assemblyand is particularly related to a crank axle of fiber-reinforcedconstruction and to the connection between a fiber-reinforced crank axleand a crank arm.

(2) Description of the Related Art

A bicycle crank assembly or crankset has traditionally been designed asa 3-piece assembly consisting of a crank axle, a left crank arm, and aright crank arm. The left crank arm is connected to the left end of thecrank axle via a system of straight and/or tapered splines incombination with a fixing bolt to secure the connection. Likewise, theright crank arm is connected to the right end of the crank axle in asimilar arrangement. The crank axle is radially supported and axiallylocated by two axially spaced bearing assemblies that are locatedaxially inboard of the crank arms. The drive sprockets, or chainrings,are mounted to the right crank arm via a “spider”, which consists of aseries of radial arms extending between the chainring and the axle endof the right crank arm. The crank axle is generally made of steel, whilethe crank arms are usually of solid aluminum construction.

More recently, some state-of-the-art designs are arranged such that thesteel crank axle is permanently fixed to the right crank arm. Inaddition, some high-end crank arms utilize carbon fiber reinforcedmaterial in their construction. However, these crank assemblies stillutilize crank axles made of steel, which is a very high-densitymaterial, and results in a crank axle that is quite heavy.

There have been some prior art cranksets that utilize a split crankaxle, where a left crank axle portion is removably connected to a rightcrank axle portion at a connection interface that is located axiallyinboard from the two supporting bearings. In such designs, the leftcrank arm is integrally joined to the left crank axle portion and theright crank arm is integrally joined to the right crank axle. Such aconnection may be considered a structural interruption of the crank axleand this type of design places this connection at a very highly stressedregion of the crank axle, which may result in a weaker and/or heavierconnection. Additionally, this region also has severe geometricconstraints due to the surrounding bottom bracket shell (not shown) ofthe bicycle frame. This serves to limit the structural geometrynecessary to create a strong and lightweight connection. Further, sincethe region of connection is completely enclosed by the bottom bracketshell and the bearings, access and means to operate the connection areseverely limited. This results in further constraints on the design ofthis connection and further limits the ability to create a rigid, strongand lightweight connection. Needless to say, such designs have had onlylimited success in the marketplace.

In addition, the connection between the crank arm(s) is somewhat complexand requires the expense of precision machining and additionalmanufacturing steps to achieve a reliable connection. Further, thisconnection requires additional components, such as fixing bolt(s), whichadd cost and weight to the overall assembly.

Further objects and advantages of the present invention will appearhereinbelow.

SUMMARY OF THE INVENTION

In accordance with the present invention, it has now been found that theforgoing objects and advantages may be readily obtained.

Bicycle racers and cycling enthusiasts are in a constant quest toincrease the performance of their equipment by reducing its weight. Thisis well known in the field and is particularly applicable to therotating components of the bicycle such as the crankset. It is an objectof the present invention to provide a bicycle crank assembly that islight in weight, preferably lighter than traditional crank assemblies,while maintaining the requisite structural integrity. It is a furtherobject of the present invention to produce a lightweight crank assemblythat can be produced economically to minimize any additional expenseassociated with the increase in performance.

The present invention utilizes a crank axle that is constructed, atleast in part, from fiber reinforced composite materials that are highin strength and light in weight. This type of material is highlyadvantageous in a crank axle application. In addition, it is preferablethat the crank axle and at least one of the crank arms be molded as onecontiguous unit.

Fiber reinforced composite materials possess very favorable structuralproperties, such as very high strength and stiffness, while having amuch lower density than most metals. Thus, a well-designed crank axlethat utilizes composite materials may be much lighter than a comparablesteel crank axle, while maintaining, or increasing, the requisitestructural properties.

In operation, as the pedals of the bicycle are rotated in their circularcycle, the orientation of the crank arms and the loads on the pedals areconstantly changing. Therefore, the crank axle experiences bendingstresses in multiple directions, as well as torsional stress. Bycarefully orienting the fiber reinforcement of the crank axle, it ispossible to adjust the structural properties of the finished crank axleto be highly optimized for the loading and stresses unique the crankaxle application. This permits the structural properties to be optimizedwhile minimizing material usage, thereby further reducing the weight andcost of the crank axle.

The present invention includes embodiments where the crank axle isformed as a contiguous unit with one or both of the crank arms. Incomparison with conventional crank assemblies, the present invention maybe easily adapted to this type of arrangement. Because the compositematerial is highly moldable, it is relatively easy to create thegeometry required to create such a contiguous crank arm and crank axle.Such geometry would be far more difficult to achieve using metalconstruction. Further, because the crank axle may be constructed fromlayers or plies of composite material, these layers may be interleavedwith the plies of a composite crank arm to create a high strength andlightweight contiguous connection between these two components.

Further, the present invention describes a hollow crank arm and a hollowcrank axle. It is well understood that, by locating the structuralmaterial away from the neutral axis, a hollow crank arm and/or crankaxle may be significantly stronger and lighter than a correspondingsolid component as utilized in conventional crank assemblies.

In contrast to split crank axle designs, the present invention utilizesa crank axle that spans between the two axially spaced supportingbearings without structural interruption. In embodiments where aremovable connection is required, such as the connection between thecrank arm and an extending end portion of the crank axle, this isaccomplished outside of the confines of the bottom bracket shell.Therefore the aforementioned geometric constraints of an enclosedconnection do not exist and a robust and lightweight connection may beachieved. Further, since the crank axle is not split, the fibers may becontinuous and may extend between the bearings, which allows the presentinvention to take full advantage of the mechanical properties of thismaterial, while minimizing the amount of material (and weight) required.

The contiguous crank arm and crank axle embodiments of the presentinvention also serve to eliminate the “doubling” geometry of aconventional crank assembly where crank arm is overlapping the end ofthe crank axle, resulting in a comparatively heavy double wall to effectthe crank arm-to-crank axle connection. Further, the contiguous crankarm and crank axle unit of the present invention eliminates the fixingbolt and related hardware of conventional crank assemblies, therebyeliminating their associated weight and expense. Still further, thesplined connection between the conventional crank arm and crank axleassembly require a precision fit. The fabrication involved in thisprecision fit, as well as the machining to accept the fixing bolt addsexpense to the conventional assembly. This cost is eliminated incontiguous crank arm and crank axle unit of the present invention.

Further features of the present invention will become apparent fromconsidering the drawings and ensuing description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more readily understandable from aconsideration of the accompanying exemplificative drawings, wherein:

FIG. 1 a is a perspective view schematically illustrating the generalconfiguration of a crank axle;

FIG. 1 b is a radial plan view the general configuration of the crankaxle of FIG. 1 a;

FIG. 1 c is a cross-section view of the crank axle of FIG. 1 a as seengenerally in the direction 3-3 of FIG. 1 b, including a bearing;

FIG. 1 d is a partial cross section view showing the crank axle of FIGS.1 a-c, as assembled with bearings, crank arms and bottom bracket shell;

FIG. 2 a is a perspective view schematically illustrating the fiberalignment of a tubular fiber-reinforced molding charge;

FIGS. 2 b-e are diagrammatic views, describing fiber reinforcement andillustrating fiber orientations of 0°, 90°, 45° and 135° respectively.

FIG. 3 a is a partial cross-section view of a crank axle offiber-reinforced material, including bearings;

FIG. 3 b is a partial cross-section view of a crank axle offiber-reinforced material, including an external bearing interfaceinsert and an internal threaded insert;

FIG. 3 c is a partial cross-section view of a crank axle offiber-reinforced material, including a combined crank arm interface andbearing interface insert;

FIG. 3 d is a partial cross-section view of a crank axle offiber-reinforced material, including a crank arm interface insert;

FIG. 4 a is a perspective exploded view of an additional embodiment ofthe present invention, schematically illustrating the assembly of anintegral right crank arm and crank axle component with a left crank armcomponent;

FIG. 4 b is a radial plan view of the assembly of FIG. 4 a;

FIG. 4 c is a partial cross section view of the embodiment of FIG. 4 aas seen generally in the direction 5-5 of FIG. 4 a;

FIG. 4 d is a partial cross section view of the embodiment of FIG. 4 aas seen generally in the direction 7-7 of FIG. 4 b;

FIG. 4 e is a partial cross section view of the embodiment of FIG. 4 aas seen generally in the direction 9-9 of FIG. 4 b;

FIG. 5 a is a partial cross section view of an additional embodiment ofthe present invention in a view roughly corresponding to FIG. 4 c;

FIG. 5 b is a partial cross section view of the embodiment of FIG. 5 ain a view roughly corresponding to FIG. 4 d;

FIG. 6 a is a perspective exploded view of an additional embodiment ofthe present invention, schematically illustrating the assembly of anintegral right crank arm and crank axle component with a left crank armcomponent;

FIG. 6 b is a radial cross-sectional view of the integral right crankarm and crank axle component of FIG. 6 a as seen generally in thedirection 11-11 of FIG. 6 a;

FIG. 6 c is a partial cross section view of the embodiment of FIG. 6 aas seen generally in the direction 13-13 of FIG. 6 b;

FIG. 6 d is a partial cross section view of the embodiment of FIG. 6 aas seen generally in the direction 15-15 of FIG. 6 b;

FIG. 7 a is a perspective view of an additional embodiment of thepresent invention, schematically illustrating an integral right crankarm and crank axle and left crank arm component;

FIG. 7 b is an axial plan view of the integral crank embodiment of FIG.7 a;

FIG. 7 c is a radial plan view of the integral crank assembly of FIG. 7a, shown in partial cross section as seen generally in the direction17-17;

FIG. 7 d is a partial cross section view of the crank axle of FIG. 7 aas seen generally in the direction 19-19 of FIG. 7 c;

FIG. 7 e is a partial cross section view of the right crank arm of FIG.7 a as seen generally in the direction 21-21 of FIG. 7 c;

FIG. 7 f is a partial cross section view of the left crank arm of FIG. 7a as seen generally in the direction 23-23 of FIG. 7 c;

FIG. 8 is a radial cross section view of an additional embodiment of thepresent invention, including an integral crank arm and crank axle, andincluding supporting bearings and a reinforcement insert.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 a-c describe a prior art crank axle 4. For the sake oforientation convention, the crank axle 4 may be considered as agenerally cylindrical component that has a longitudinal or axial axis 8about which it rotates. The axial direction 10 is a direction parallelto the axial axis 8. The radial direction 12 is a direction extendingradially and perpendicular to the axial axis 8. The tangential direction13 is a direction tangential about the axial axis 8 at a radial distancefrom the axial axis 8. The term “axially inboard” refers to an axiallocation proximal to a point on the axial axis 8 that is generallymidway between bearing surfaces 14 a and 14 b. Conversely, the term“axially outboard” refers to an orientation that is distal from thispoint. Similarly, “radially inboard” refers to an orientation proximalto the axial axis 8 and “radially outboard” refers to an orientationdistal to the axial axis 8.

Crank axle 4 has relatively conventional geometry and includes splinedportions 16 a and 16 b with splines 11 that extend axially for matingwith crank arms (not shown) in the conventional manner. Cylindricalbearing surfaces 14 a and 14 b are surfaces that are adapted for fitmentof bearing assemblies 22 a and 22 b respectively. Bearing surfaces 14 aand 14 b may be designed to serve directly as inner bearing races orthey may be adapted to fit an inner bearing race 24 of a bearingassembly 22 a and/or 22 b (as shown in FIG. 1 c). It is understood thatbearing surfaces 14 a and 14 b may possess any geometry or profilecontour that is beneficial to adapt to their specific bearingapplication. In FIG. 1 b, these bearing surfaces 14 a and 14 b are shownto be cylindrical surfaces, with corresponding shoulders 18 a and 18 bfor axial location of mating bearing assemblies 22 a and 22 b that areshown here to be of the cartridge bearing type. Crank axle 4 includesend faces 19 a and 19 b and internally threaded bores 20 a and 20 b forthreadable mating with crank fixing bolts (not shown) that serve tofasten the respective crank arms to the crank axle 4 in the conventionalmanner. Crank axle 4 is shown here to be of hollow cylindrical geometry,including a through bore 15, which is the preferred design. Conventionalcrank axles 4 are usually constructed of steel material, which tends tobe quite heavy.

It is understood that the crank axle 4 depicted in FIGS. 1 a-c is of arepresentative crank axle geometry that is utilized elsewhere in thisspecification. However, the requirements of a specific application mayrequire adaptation of wide range of crank axle geometries notspecifically described here. In general, a crank axle need only be agenerally cylindrical element with provision for mounting two axiallyspaced crank arms and provision for at least two axially spacedbearings. Alternatively, splined portions 16 a and 16 b may have a widerange of geometries adapted for connection with a crank arm such thatrotational torque may be transmitted between the crank axle and themating crank arm. Also, bearing surfaces 14 a and 14 b may also have awide range of geometries adapted to facilitate easy rotation of thecrank axle 4. Threaded bores 20 a and 20 b are simply provided as arepresentative means to secure a crank arm to the crank axle 4 and awide range of alternative means may be envisioned.

FIG. 1 d shows a typical assembly of the crank axle 4 of FIGS. 1 a-cwith two axially spaced bearing assemblies 22 a and 22 b that aremounted within a bottom bracket shell 6 of the bicycle frame (notshown). Left crank arm 7 is rotationally engaged to the left end of thecrank axle 4 via splined portion 16 a and secured in place by the fixingbolt 21 a. Left crank arm 7 is thus axially and rotationally locked tocrank axle 4. Similarly, right crank arm 9 is engaged to the right endof the crank axle 4 via splined portions 16 b and secured in place bythe fixing bolt 21 b.

In the case of fiber-reinforced components, it is generally understoodthat fiber orientation plays a large role in the structural performanceof the component. Fiber-reinforced components generally have greaterstrength and stiffness in a direction parallel to the alignment of thefibers and lesser strength and stiffness in a direction perpendicular tothe alignment of the fibers. Therefore it is preferable to orient thefibers in one direction or in several directions to optimize thestructural performance for the final intended end use of the product.The example shown in FIGS. 2 a-e shows how a cylindrical component, suchas a crank axle, may be constructed or formed from multiple layers orplies of fiber-reinforced material of a variety of fiber orientations.As an example for illustration purposes, FIG. 2 a shows how acylindrical shape may be created by rolling plies or flat fiberreinforced sheet 30 into a cylindrical pre-form 32 that may subsequentlybe molded to create the corresponding cylindrical crank axle asdescribed in FIGS. 3 a-e.

FIG. 2 a shows the reinforcement fibers of the fiber-reinforced sheet 30to be oriented at 0°, since these fibers are parallel to the axial axis8. Additionally or alternatively, a wide range of fiber orientations maybe utilized, as illustrated in FIGS. 2 b-e. In this example, the 0°fibers of FIG. 2 b will tend to impart bending strength and axialtensile strength to the crank axle 4. The 90° fibers of FIG. 2 c willtend to impart hoop strength and crush strength to the crank axle 4. The45° and 135° fibers of FIG. 2 d and FIG. 2 e will tend to impartbidirectional torsional strength to the crank axle 4. Severalfiber-reinforced sheets of a variety of fiber orientations may belaminated or woven together to create an optimized combination ofproperties. For a crank axle 4 application it is advantageous to includefibers in a generally 45° and 135° orientation. This aligns the fibersin a helical orientation to provide the requisite torsional strength andstiffness for a crank axle application.

The example shown in FIG. 2 a show a “roll-wrapping” technique, which ismerely one example of a fabrication technique shown here merely toillustrate the importance of fiber orientation. In FIGS. 2 a-d, thefiber-reinforced sheet 30 is shown to be a “prepreg” sheet ofreinforcing fiber that is pre-combined with uncured resin.Alternatively, a wide range of fiber types, fiber-reinforced startingmaterials, fiber lengths, fiber orientations and fabrication processesmay be employed to construct a fiber-reinforced component.

FIG. 3 a shows crank axle 40 that is constructed entirely offiber-reinforced material, which has excellent structural properties andis has a significantly lower density than steel for a significantreduction in weight. It is preferable that the fiber-reinforced materialconsist of fibers in a polymer resin matrix, where the matrix serves tobind the fibers together and also to transmit shear loads betweenadjacent fibers. It is generally understood that longer fibers result ingreater structural performance in comparison to shorter fibers. Thus itis also preferable that these fibers be generally continuous, ratherthan discontinuous or “short” fibers, thereby providing a strengthadvantage. It is further preferable that these fibers be characterizedas high-strength fibers, such as carbon fibers, aramid fibers,liquid-crystal fibers, PBO fibers, etc. Of these fiber types, carbonfibers generally possess the best performance characteristics for thisapplication. The resin matrix may be a thermoset resin, such as epoxy orvinylester or it may be a thermoplastic resin such as polyamide,polyester or any of a wide range of available thermoplastic resins.Fiber reinforced materials as described here may also be termed“composite” material or, in the case where high-strength fibers areused, they may also be termed “advanced composite”. There is a widerange of manufacturing processes by which a fiber reinforced crank axlemay be produced. These processes are well known in industry and mayinclude filament winding, roll wrapping, resin transfer molding, bladdermolding, compression molding, prepreg layup, wet layup, among others.However, it should also be understood that these advanced compositematerials are on the cutting edge of technology and new fibers, resins,and manufacturing processes are continually being developed that may beapplicable to the present invention.

Crank axle 40 of FIG. 3 a includes cylindrical bearing surfaces 42 a and42 b with corresponding shoulders 44 a and 44 b for axial location ofmating bearing assemblies 22 a and 22 b that are shown here to be of thecartridge bearing type. Crank axle 40 includes end faces 48 a and 48 band internally threaded bores 50 a and 50 b for threadable mating withcorresponding crank bolts (not shown) that serve to fasten thecorresponding crank arms to the crank axle 40. Crank axle 40 is shownhere to be of hollow cylindrical geometry, including a through bore 52,which is the preferred design. However, it is also envisioned that thebore 52 of the crank axle may alternatively include internal closed-offportions or may be filled with low-density material such as foam. Afurther alternative design may be of generally solid construction.

It should be noted that the crank axle 40 is a continuous crank axlethat extends to pass through the two axially spaced radial bearingassemblies 22 a and 22 b. This is the preferred arrangement, since itpermits continuous and uninterrupted structural geometry to extendbetween these radial supporting locations. This serves to minimize oreliminate any structural interruptions or weaknesses in this highlystressed region. This is in contrast to split axle designs where thediscontinuous crank axle is split or otherwise connected together,resulting in a weakened region adjacent the or between the bearingassemblies 22 a and 22 b. Further, it is preferable that long orcontinuous fiber reinforcement be utilized in fabrication of the crankaxle 40. To maximize structural properties, this continuous fiber mayextend, generally without interruption, through the axial length of thecontinuous crank axle to thereby optimize its structural properties inthis highly stressed region.

To provide the optimal structural properties of the crank axle 40, it isgenerally preferable to design the crank axle to be as large a diameteras geometrical constraints will permit. A larger diameter crank axle 40may be designed to be lighter and/or have higher structural propertiesin comparison with a smaller diameter crank axle 40. Given currentbicycle frame geometry, it is preferable that the crank axle 40 has anoutside diameter in the range of 22 mm to 35 mm.

While the term “hollow” generally connotes an outer structural shellthat surrounds a cavity, it is common for advanced composite componentsto utilize a low-density material, such as foam or other core materialto fill or partially fill the cavity. These low-density “core materials”generally work in compression to provide crush strength to the finishedcomponent and/or to connect opposite walls of the structural shell. Suchcore materials may provide increased structural performance when thestructural shell is not completely self-supporting. For the purposes ofdescribing the present invention, the term “hollow” may include a cavityfilled with a low-density core material.

While fiber-reinforced material has many excellent structuralproperties, it does not necessarily have high hardness characteristics.Also, depending on the geometry and processing involved, it may bedifficult to maintain these elevated structural properties in regions ofabrupt geometry changes. For these reasons, it may be advantageous toadd pre-formed inserts to the fiber-reinforced crank axle to maintainthe desired structural properties or to provide a region of higherhardness. These inserts may simply be subcomponents that are made fromfiber reinforced material and then bonded or otherwise joined to thecrank axle. These inserts may also be insert-molded with the crank axleduring molding of the fiber-reinforced portion. In this case, the matrixresin is adhered to the insert to create an integrally joined connectionbetween the fiber reinforced crank axle portion and the insert portion.Alternatively, it may be preferable to integrally join the insert to thecrank axle by adhesively bonding the two subcomponents. To insure astrong joinder, it is generally advisable to provide sufficient bondingsurface area of overlap between the two subcomponents. Often, it isdesirable to produce these inserts from a lightweight metallic materialsuch as aluminum or titanium. These metallic materials are isotropic andmay be easily machined to provide highly detailed geometry and alsopossess higher hardness than many composite materials. Additionally,hardened steel inserts may be utilized to create an integral bearingrace circumferentially surrounding the crank axle.

FIGS. 3 b-d describe a range of exemplary crank axle configurations thateach utilize an insert(s) as previously discussed. FIG. 3 b describescrank axle assembly 60 that utilizes an annular bearing insert 62, whichincludes cylindrical bearing surface 64 and shoulder 66.Fiber-reinforced crank axle body 68 is a generally cylindrical elementthat extends axially through the annular bearing insert 62. Insert 62 isshown here to be adapted to fitment of the inner race of a bearingassembly (not shown). Alternatively, bearing insert 62 may be designedas an integral bearing race where a bearing, such as a rolling orsliding element, is in direct contact with the bearing insert 62. Inthis respect, bearing insert 62 may be considered to be a bearinginterface insert. Crank axle 60 is otherwise similar to crank axle 40.It should be noted that bearing insert 62 is an external insert thatcompletely circumscribes the outside diameter of the fiber-reinforcedcrank axle body 68.

Additionally, crank axle assembly 60 includes a threaded insert 63 withinternal threads 65 for threadable connection with a fixing bolt (notshown). Threaded insert 63 is integrally adhered to the fiber-reinforcedcrank axle body 68 at a joining interface 67. It should be noted thatthreaded insert 63 is an internal insert that is completelycircumscribed by the inside diameter of the fiber-reinforced crank axlebody 68.

FIG. 3 c describes a crank axle assembly 70 that utilizes a splineinsert 72, including spline surface 74 and inside diameter 75. Splineinsert 72 also includes bearing surface 76 and shoulder 78 for fitmentof a bearing assembly (not shown). The fiber reinforced crank axle body80 is a generally tubular element and includes external surface 82. Thepre-formed spline insert 72 is placed in a mold during molding of thecrank axle body 80 such that the material of the crank axle body 80conforms to the inside diameter 75 of the spline insert 72 to result ina matched contour with external surface 82. During this molding process,the molding resin of the crank axle body 80 adhesively bonds to thespline insert 72 at the interface between the external surface 82 andthe inside diameter 75. Crank axle 70 is otherwise similar to crank axle40. Since the spline insert 72 also includes spline surface 74 as ameans to connect to the crank arm (not shown) in the conventionalmanner, it may be considered to be a crank arm interface insert.

FIG. 3 d describes a crank axle assembly 90 that utilizes an extensioninsert 92 that includes geometry to axially extend the fiber-reinforcedcrank axle body 102. Extension insert 92 includes internal threads 94for engagement with a fixing bolt (not shown) and external splines 96for engagement with mating internal splines of a crank arm (not shown)in the conventional manner. Extension insert 92 also includes anaxially-extending sleeve 98, which includes a cylindrical outer surface100. The fiber-reinforced crank axle body 102 is a generally tubularelement with inside diameter 104. The extension insert 92 may beadhesively bonded to the crank axle body 102 at the interface betweenthe outer surface 100 and the inside diameter 104. In comparison withthe embodiments of FIGS. 3 b-c, it should be noted that extension insert92 is an internal insert that is completely circumscribed by the insidediameter of the fiber-reinforced crank axle body 102.

It should be noted that the continuous circumscribing interfacesdescribed in FIGS. 3 b-d are not discontinuous around their matingcircumferences, but instead may be considered as closed cylindricalelements. This maintains the structural integrity of both the insert andthe crank axle and results in a more structurally efficient joinderbetween the two portions. Further, it should be noted that theembodiments of FIGS. 3 b-d are merely representative of a wide range ofpossible insert configurations that may be adapted to the presentinvention. While FIGS. 3 b-d are partial views of representativeembodiments that describe the left portion of the crank axle, it isunderstood that a right portion of the crank axle is implied and may begenerally symmetrical with the left portion.

While the previous embodiments utilize a crank axle that is a separatecomponent from its associated crank arms, it may be desirable to combinethe crank axle with one of the crank arms to create an integralassembly. The fiber reinforced crank axle may be a pre-formed elementthat is permanently joined to a pre-formed crank arm of metallic orfiber-reinforced composite construction. Alternatively, either the crankarm or the crank axle may be molded to include the corresponding crankarm or crank axle as a pre-formed molding insert. However, it isgenerally preferable that the integral crank arm be constructed ofcomposite materials and that the crank arm and crank axle be moldedtogether as one contiguous unit.

FIGS. 4 a-e describe an arrangement where right crank arm 122 ispermanently fixed to the right end 128 of crank axle 120 and the leftcrank arm 124 is removably assembled to the left end 130 of crank axle120. Left crank arm 124 includes a pedal end 112, located radiallyoutboard from the crank axle 120 and an axle end 110, located proximalto the crank axle 120. Pedal end 112 includes threaded hole 125 formounting of a left pedal (not shown) and axle end 110 includes internalsplines 134 to mate with external splines 132 of the crank axle 120. Theaxle end 110 of the left crank arm 124 is secured to crank axle 120 viacrank bolt 126 in the conventional manner. Right crank arm 122 includesa pedal end 114, located radially outboard from the crank axle 120 andan axle end 116, located proximal to the crank axle 120. Pedal end 114includes threaded hole 123 for mounting of a right pedal (not shown) andaxle end 116 is integrally connected to the crank axle 120. Crank armaxis 127 a extends along the longitudinal length of the right crank arm122 between threaded hole 123 and crank axle 120 in a generally radialdirection. Similarly, crank arm axis 127 b extends along thelongitudinal length of the left crank arm 124 between threaded hole 125and crank axle 120 in a generally radial direction Right crank arm 122is a hollow element with a fiber reinforced structural shell 142 and aninternal cavity 136. The shell 142 includes axially inboard wall 140 andaxially outboard wall 144. The sidewall 143 of the right crank arm 122extends between the inboard wall 140 and the outboard wall 144. Crankaxle 120 is a hollow tubular element with an internal cavity 138 and atubular wall 146, a portion of which intersects and extends through theinboard wall 140 to join with the outboard wall 144. While FIGS. 4 a-dshow the crank axle 120 integrally connected to the right crank arm 122,it is understood that the crank axle 120 may alternatively be integrallyconnected to the left crank arm 124.

FIG. 4 c shows that crank axle 120 also utilizes insert 152, whichincludes the internal threads 154 for engagement of the fixing bolt 126and the external splines 132 for engagement with internal splines 134 ofthe left crank arm 124. Insert 152 also includes a sleeve portion 156that is adhered or otherwise integrally joined to the inside diameter157 of the tubular wall 146. End face 158 of the crank axle 120 isexposed to provide a radially extending shoulder for axial location of abearing assembly (not shown).

It may be seen in FIG. 4 c that both the crank axle 120 and the rightcrank arm 122 are made up of plies or layers of composite material,preferably molded from prepreg, a composite material in whichreinforcement fibers, such as carbon fibers, are pre-impregnated withuncured resin, such as epoxy resin. This prepreg material is usuallysupplied in sheet form to include unidirectional or woven fibers, whichmay be wrapped and formed to achieve the desired pre-formed shape. Thispre-form is then placed in a mold (not shown) and heat and compactionpressure are applied to the prepreg to consolidate the plies and to cureout the resin, thus creating a hardened and molded structural component.Compaction pressure may be created through a variety of methods wellknown in industry. In this configuration, compaction pressure may becreated through the utilization of pressurized bladders placed withininternal cavities 136 and 138 during the molding process.

Some of the plies of the crank axle 120 are flared to overlap withmating plies of the inboard wall 140 as shown in FIG. 4 c-e. Other pliesof the crank axle 120 extend through the inboard wall 140 and internalcavity 136 and are flared to overlap with outboard wall 144. Similarly,plies of the crank arm 122 may be extended to overlap with the plies ofthe crank axle 120. Further, additional plies may be arranged to spanacross the juncture between the crank axle 120 and the right crank arm122. In this way, plies of continuous fiber are interleaved and extendto span across the joint or interface between the crank axle 120 and theright crank arm 122, thus significantly reinforcing the integralconnection between these two components. Foam plug 148 is located in theinternal cavity 138 adjacent the right crank arm 122. A first internalbladder (not shown) is placed within internal cavity 136 and a secondinternal bladder (not shown) is placed within cavity 138. The entireperform is placed within a mold cavity (not shown) that defines theexternal geometry of the right crank arm 122 and the crank axle. Thefirst bladder is wrapped around the crank axle 120 in the regionadjacent the right crank arm and the foam plug 148 serves to maintainthe internal shape of the crank axle 120 during molding. The mold isthen heated and the bladders are pressurized with air such that theplies are consolidated and the resin is cured. Such a bladder-moldingprocess is well known in industry. The crank axle 120 and the crank arm122 are thus co-molded and integrally joined. It may also be seen inFIGS. 4 d-e that crank arm 122 also includes an internal wall or septum150 that spans between inboard wall 140 and outboard wall 144. Thisseptum 150 serves to provide a rigid link between the inboard wall 140and outboard wall 144, thus providing greater structural integrity tothe right crank arm 122. Internal cavity 136 is also shown to extend towrap around the crank axle 120 as shown in FIGS. 4 c-d.

While the bladder molding process as described above may be thepreferred molding method to produce the crank arm 122 and crank axle 120assembly, several alternate molding methods may be employed, includingresin transfer molding, filament winding, trapped silicone molding.Further, while hollow internal cavities 136 and 138 are shown here,these cavities may alternatively be filled with foam or otherlow-density material.

While FIGS. 4 c-d shows internal cavity 136 to wrap around the crankaxle 120, it is also envisioned that a portion of the wall of the crankaxle may be shared with a portion of the wall of the crank arm 122 asshown in FIGS. 5 a-b. FIG. 5 a roughly corresponds to FIG. 4 c and showsthe plies of the crank axle 160 to be collinear and nested to overlapwith the plies of the sidewall 162 of right crank arm 164. In contrastto the embodiment of FIGS. 4 a-e, internal cavity 166 of the right crankarm 164 does not wrap completely around the crank axle 160, nor does itinclude a septum. It may be seen in FIGS. 5 a-b that plies of the crankaxle 160 are interleaved with plies of the crank arm 164 and vice-versa.Crank axle 160 includes internal cavity 168 and foam plug 161, whichserves to support the surrounding plies of fiber-reinforced materialduring molding and to provide compressive and crush strength to thecrank axle 160 in this region. Bladders may be placed within internalcavities 168 and 166 and the molding process previously described may beutilized to co-mold and integrally connect the crank axle 160 and rightcrank arm 164.

As an alternative to the co-molded construction described in theembodiments of FIGS. 4 a-e and FIGS. 5 a-b, it is also envisioned thatthe crank arm and/or the crank axle may be pre-formed elements. Forinstance, the crank axle may be a preformed element that serves as aninsert in a crank arm molding process. Thus the crank arm is molded tooverlap and adhere with at least a portion of the pre-formed crank axle.When the crank arm is solidified, an integral connection between thecrank arm and the crank axle is thus created. Alternatively, the crankarm may be a pre-formed element that serves as an insert in a crank axlemolding process. Thus the crank arm is molded to overlap and adhere withat least a portion of the pre-formed crank arm. When the crank axle issolidified, an integral connection between the crank axle and the crankarm is thus created. A further alternative may utilize both a pre-formedcrank axle and a pre-formed crank arm. In this case, the pre-formedcrank axle and a pre-formed crank arm may be adhesively bonded orotherwise joined together at an interface between the two to create anintegral connection between the two pre-formed components.

Whereas the embodiment of FIGS. 4 a-d show the geometry of the crankaxle 120 to intersect with the geometry of the crank arm 122, theembodiment of FIGS. 6 a-d show the cylindrical walls 184 of the crankaxle 180 to extend continuously to form the perimeter sidewalls 186 ofthe right crank arm 182. Thus the integral combination of the crank axle180 and the crank arm 182 may be viewed as a continuous L-shaped tubularelement, including a bent region 188. In the case where these componentsare bladder-molded, a single continuous bladder may be utilized to formboth the crank axle 180 and the crank arm 182. It is also preferable tocreate a continuous septum 190 that extends along the length of theright crank arm 182 to rigidly connect the inboard wall 192 and theoutboard wall 194 to prevent independent movement between the opposingwall portions and thereby increase the structural integrity of the rightcrank arm 182. Septum 190 further extends through bent region 188 andthrough the crank axle 180 to provide reinforcement to these portions aswell.

Crank axle 180 axle also includes an annular pre-formed flange insert193 that includes an axially extending cylindrical bearing portion 195for mounting of a cartridge bearing assembly (not shown) and a radiallyextending flange portion 196 with threaded holes 198 for connection withthe drive sprocket (not shown) commonly associated with crank arms. Itis understood that flange portion 196 merely shows one representativemethod for connecting a drive sprocket to the crank arm 182. A widerange of alternate methods may be substituted, including integrallymolding a flange to the crank axle 180 or to the crank arm 182 forconnection with the drive sprocket(s). Crank axle 180 also includesexternal splines 187 for engagement with internal splines 189 of leftcrank arm 185 in the manner previously described.

FIGS. 7 a-e describe an embodiment where both the right crank arm 202and the left crank arm 204 are each integrally connected to the crankaxle 200 in a manner similar to that described in FIGS. 6 a-d. Thus thecrank assembly 206 includes the integral combination of the crank axle200, the right crank arm 202 and the left crank arm 204 and may beviewed as a continuous S-shaped tubular element, including bent region208 between the right crank arm 202 and the crank axle 200 and bentregion 210 between the left crank arm 204 and the crank axle 200. It isalso preferable to create a continuous septum 220 that extends throughcrank axle 200 and bent regions 208 and 210 and through at least aportion of right crank arm 202 and left crank arm 204. This may beconsidered as one of the lightest and most structurally efficient crankassembly arrangements. Crank axle 200 also includes external bearinginserts 212 a and 212 b for mounting of cartridge bearing assemblies(not shown).

FIG. 8 describes an embodiment similar to FIG. 6 b, however the crankaxle 224 is a hybrid crank axle that is composed of fiber-reinforcedportion 226 and an insert portion 228. Thus the fiber reinforced portion226 and the insert portion 228 are overlapped and adhered to each otheralong their contacting interface that extends over essentially theentire length of the crank axle 224, resulting in an integral joinderbetween the two. Having such a large overlapping surface are between theinsert portion 228 and the fiber reinforced portion 226 permits a largeradhered interface are for a stronger integral connection between thetwo. Further, insert portion 228 provides reinforcement of thefiber-reinforced portion 226, and vice-versa, providing additionalstrength in this highly stressed region. To this degree, insert portion228 may be considered to be a reinforcement insert. Insert portion 228includes bearing surfaces 222 a and 222 b and extends between supportingbearing assemblies 22 a and 22 b. Insert portion 228 also includes aspider 230 for fitment of the drive sprockets (not shown) and a splinedportion 232 for fitment of a left crank arm (not shown) and a threadedhole 223 to mate with a fixing bolt (not shown). Insert portion 228 alsoincludes shoulder flange 225 for axial location of bearing assembly 22 aand shoulder 227 for axial location of bearing assembly 22 b.Fiber-reinforced portion 226 is contiguous with the right crank arm 234and is a hollow element with internal cavity 236. The cylindrical wallsof the fiber-reinforced portion 226 extend continuously to form rightcrank arm 234, including bent portion 235. Thus, the crank axle 224 isintegral and contiguous with the right crank arm 234.

It should be noted that the interface between the insert portion 228 andthe fiber-reinforced portion 224 is a tapered conical surface with thelarger diameter adjacent the contiguous right crank arm 234. Thispermits the maximum possible diameter of the fiber-reinforced portion226 to provide the highest strength in the most highly stressed regionadjacent the junction between the crank axle 224. Likewise, this permitsthe wall thickness of the insert portion 228 to be thicker in the regionadjacent the left crank arm (not shown). The outside diameter of bearingsurface 222 b corresponds with the inside diameter 238 of bearingassembly 22 b. Likewise, the outside diameter of bearing surface 222 acorresponds with the inside diameter 240 of bearing assembly 22 a. Itshould be noted that inside diameter 238 is larger than the insidediameter 240, thus permitting a still larger diameter of thefiber-reinforced portion 226 and further increasing the strength in thehighly stressed region adjacent the junction between the crank axle 224.Thus the inside diameter 238 of bearing assembly 22 b is larger than theinside diameter 240 of bearing assembly 22 a. This permits the shoulderflange 225 to be assembled through the inside diameter 238 of thebearing assembly 22 b, yet still be sized to have axial locatingengagement with the inner race of the smaller bearing assembly 22 a.

While my above description contains many specificities, these should notbe construed as limitations on the scope of the invention, but rather asexemplifications of embodiments thereof. It is to be understood that theinvention is not limited to the illustrations described and shownherein, which are deemed to be merely illustrative of the best modes ofcarrying out the invention, and which are susceptible of modification ofform, size, arrangement of parts and details of operation. For example:

The reinforcement insert portion 228 of FIG. 8 is shown to be anexternal insert that is surrounded by a fiber-reinforced portion 226 ofthe crank axle. Additionally or alternatively, it is also envisionedthat a reinforcement insert may be an internal insert that is at leastpartially surrounded by a fiber-reinforced portion of the crank axle.

The inserts described in FIGS. 3 a-d and FIG. 8 show a series of insertsthat have a continuous circumscribing joining interface with theircorresponding fiber-reinforced crank axle portions. However it is alsoenvisioned that this interface may be discontinuous or interrupted suchthat this joining interface is not continuously circumferential aboutthe axial axis. For example, the insert may contain a series of axiallyextending projections with gaps in between. Thus, a joining interfacebetween the projections and the fiber-reinforced crank axle portionwould be interrupted by these gaps.

The embodiments of FIGS. 4 a-e, 5 a-b, 6 a-d, 7 a-f, 8 all describe anintegrated crank arm and crank axle combination. It has been describedhow the crank arm and crank axle may be co-molded to create thisintegrated unit. However, it is also envisioned that the crank axleand/or the crank arm may be pre-formed elements that are integrallyjoined together.

The embodiment of FIGS. 6 a-d describes a flange adapted to connect adrive sprocket to the right crank arm. It is also envisioned that thedrive sprocket may instead be directly or indirectly connected to theleft crank arm or to the crank axle.

It is to be understood that the invention is not limited to theillustrations described and shown herein, which are deemed to be merelyillustrative of the best modes of carrying out the invention, and whichare susceptible of modification of form, size, arrangement of parts anddetails of operation. The invention rather is intended to encompass allsuch modifications that are within its spirit and scope as defined bythe claims.

1. A bicycle crankshaft assembly comprising: a crank axle including anaxial axis, a first axle end, and a second axle end axially opposed tosaid first axle end; a first crank arm connected to said crank axle at afirst crank arm interface adjacent said first axle end; a second crankarm connected to said crank axle at a second crank arm interface axiallyspaced from said first crank arm interface; a first bearing surroundingsaid crank axle adjacent said first axle end for rotation of said crankaxle about said axial axis; a second bearing surrounding said crank axlefor rotation of said crank axle about said axial axis, wherein: saidsecond bearing is axially spaced from said first bearing; said crankaxle includes reinforcement fibers for structural reinforcement of saidcrank axle; and said crank axle is an integral crank axle thatsimultaneously contacts both said first bearing and said second bearing.2. A bicycle crankshaft assembly according to claim 1, wherein saidcrank axle extends through said first bearing and contacts said secondbearing.
 3. A bicycle crankshaft assembly according to claim 1, whereinsaid crank axle extends through said first bearing and extends throughsaid second bearing.
 4. A bicycle crankshaft assembly according to claim1, wherein at least a portion of said reinforcement fibers extend in ahelical direction about said axle axis.
 5. A bicycle crankshaft assemblyaccording to claim 3, wherein a first portion of said reinforcementfibers are aligned to extend in a helical direction with a helix angleof approximately 45 degrees and wherein a second portion of saidreinforcement fibers are aligned to extend in a helical direction with ahelix angle of approximately 135 degrees.
 6. A bicycle crankshaftassembly according to claim 1, wherein at least a portion of saidreinforcement fibers are generally continuous reinforcement fibers.
 7. Abicycle crankshaft assembly according to claim 6, wherein at least aportion of said continuous reinforcement fibers pass adjacent said firstbearing and extend to pass adjacent said second bearing.
 8. A bicyclecrankshaft assembly according to claim 1, wherein at least a portion ofsaid reinforcement fibers extend to at least one of said first crank arminterface and said second crank arm interface.
 9. A bicycle crankshaftassembly according to claim 1, wherein at least a portion of saidreinforcement fibers are carbon fibers.
 10. A bicycle crankshaftassembly according to claim 1, wherein at least a portion of saidreinforcement fibers are within a polymer matrix.
 11. A bicyclecrankshaft assembly according to claim 1, including an insert integrallyjoined to said crank axle.
 12. A bicycle crankshaft assembly accordingto claim 11, wherein said insert is a crank arm interface insert tointerface with at least one of said first crank arm and said secondcrank arm.
 13. A bicycle crankshaft assembly according to claim 11,wherein said insert is a bearing interface insert to interface with atleast one of said first bearing and said second bearing.
 14. A bicyclecrankshaft assembly according to claim 11, wherein said insert is athreaded insert that is operative to connect said crank axle to at leastone of said first crank arm and said second crank arm.
 15. A bicyclecrankshaft assembly according to claim 11, wherein said insert is areinforcement insert, wherein said reinforcement insert serves tostructurally reinforce said crank axle.
 16. A bicycle crankshaftassembly according to claim 11, wherein said insert is an externalinsert that is circumferentially surrounded by a portion of saidreinforcement fibers.
 17. A bicycle crankshaft assembly according toclaim 11, wherein said insert is an internal insert thatcircumferentially surrounds a portion of said reinforcement fibers. 18.A bicycle crankshaft assembly according to claim 11, wherein said insertis an extension insert, wherein said extension insert serves to axiallyextend said crank axle.
 19. A bicycle crankshaft assembly according toclaim 1, wherein said crank axle includes a shoulder for axial locationof one of at least one of said first bearing and said second bearing.20. A bicycle crankshaft assembly according to claim 1, wherein saidcrank axle constitutes a structurally hollow element with a structuralouter shell and an axially extending central hollow core, wherein saidcentral hollow core extends axially through said first bearing and saidsecond bearing.
 21. A bicycle crankshaft assembly according to claim 20,wherein said central hollow core includes low-density material.
 22. Abicycle crankshaft assembly according to claim 20, wherein said centralhollow core includes a structural septum web.
 23. A bicycle crankshaftassembly according to claim 22, wherein said septum web is aligned to begenerally parallel to the longitudinal axis of at least one of saidfirst crank arm and said second crank arm.
 24. A bicycle crankshaftassembly according to claim 1, wherein said first crank arm isintegrally joined with said crank axle.
 25. A bicycle crankshaftassembly according to claim 24, wherein at least a portion of saidreinforcement fibers are within a polymer matrix and wherein said firstcrank arm is co-molded with said crank axle.
 26. A bicycle crankshaftassembly according to claim 24, wherein at least one of said crank axleand said first crank arm is a pre-formed element.
 27. A bicyclecrankshaft assembly according to claim 24, wherein said crank armincludes reinforcement fibers and wherein at least one of (1) saidreinforcement fibers of said crank axle extend within said first crankarm and (2) said reinforcement fibers of said first crank arm extendwithin said crank axle.
 28. A bicycle crankshaft assembly according toclaim 25, wherein said reinforcement fibers of said crank axle overlapsaid reinforcement fibers of said first crank arm.
 29. A bicyclecrankshaft assembly according to claim 24, wherein said first crank armis a hollow crank arm with an internal cavity and an outer structuralshell.
 30. A bicycle crankshaft assembly according to claim 29, whereinsaid crank axle intersects with said crank arm such that said crank axleextends through a first structural wall of said first crank arm to asecond structural wall of said first crank arm, wherein said secondstructural wall is axially outboard from said first structural wall. 31.A bicycle crankshaft assembly according to claim 24, wherein said crankaxle constitutes a structurally hollow element with a structural outershell and an axially extending central hollow cavity and wherein saidfirst crank arm constitutes a structurally hollow element with astructural outer shell and wherein said outer shell of said crank arm iscontinuous with the outer shell of said crank axle.
 32. A bicyclecrankshaft assembly according to claim 24, wherein said first crank armis a hollow crank arm and includes a bladder.
 33. A bicycle crankshaftassembly according to claim 24, wherein said first crank arm includes astructural septum web and wherein said crank axle includes a structuralseptum web and wherein said septum web of said crank axle is contiguouswith said septum web of said first crank arm.
 34. A bicycle crankshaftassembly according to claim 24, wherein said crank axle includes a lowdensity reinforcement insert adjacent said first crank arm interface,wherein said reinforcement insert serves to provide crush reinforcementto the crank axle.
 35. A bicycle crankshaft assembly according to claim1, wherein said first crank arm is integral with said crank axle at saidfirst axle end and wherein said second crank arm is integral with saidcrank axle at said second axle end.
 36. A bicycle crankshaft assemblyaccording to claim 35, wherein said crank axle constitutes astructurally hollow element with a structural outer shell and an axiallyextending central hollow cavity and wherein said first crank arm is ahollow crank arm with an internal cavity and an outer structural shelland wherein said wherein said second crank arm is a hollow crank armwith an internal cavity and an outer structural shell and wherein saidcentral hollow cavity of said crank axle communicates with said internalcavities of said first crank arm and said second crank arm.
 37. Abicycle crankshaft assembly according to claim 35, wherein said firstcrank arm, said second crank arm and said crank axle constitute agenerally S-shaped crankshaft assembly.
 38. A bicycle crankshaftassembly according to claim 1, wherein said first bearing has an insidediameter and said second bearing has an inside diameter and wherein theinside diameter of said first bearing is larger than the inside diameterof said second bearing.
 39. A bicycle crankshaft assembly according toclaim 1, including a flange adapted to a drive sprocket, wherein saidflange is joined to at least one of said crank axle, said first crankarm and said second crank arm.
 40. A bicycle crankshaft assemblycomprising: a crank axle including an axial axle axis, a first axle end,and a second axle end axially opposed to said first axle end; a firstcrank arm connected to said crank axle at a first crank arm interfaceadjacent said first axle end; a second crank arm connected to said crankaxle at a second crank arm interface axially opposed to said first crankarm interface; a first bearing surrounding said crank axle adjacent saidfirst axle end for rotation about said axial axle axis; a second bearingsurrounding said crank axle axially separated from said first bearing;wherein said crank axle and said first crank arm and said second crankarm constitute a generally continuous hollow element having a generallyS-shaped configuration.